Add size check for PaintLayer

third_party/WebKit/Source/core/paint/PaintLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 76 matching lines @@
 #include "platform/transforms/TranslateTransformOperation.h"
 #include "public/platform/Platform.h"
 #include "wtf/Partitions.h"
 #include "wtf/StdLibExtras.h"
 #include "wtf/text/CString.h"
 
 namespace blink {
 
 namespace {
 
+#if !OS(WIN) // Compiler on windows seems to combine bit fields of inner structs.
+
+struct SameSizeAsPaintLayer {
+    virtual ~SameSizeAsPaintLayer() { } // Allocate vtable pointer.
+    int type;
+    int bitFields;
+    void* pointers[13];
+    LayoutUnit layoutUnits[8];
+    int intFields[6];
+    uint64_t compositingReasons[2];
+    struct {
+        IntRect rect;
+        void* pointers[8];
+        int bitFields;
+    } ancestorCompositingInputs;
+    struct {
+        int bitFields;
+    } descendantCompositingInputs;
+    struct {
+        void* pointers[2];
+    } clipper;
+    struct {
+        IntSize size;
+        void* pointer;
+        LayoutRect rect;
+    } previousPaintStatus;
+};
+
+static_assert(sizeof(PaintLayer) == sizeof(SameSizeAsPaintLayer), "PaintLayer should stay small");
+
+#endif // !OS(WIN)
+
 static CompositingQueryMode gCompositingQueryMode =
     CompositingQueriesAreOnlyAllowedInCertainDocumentLifecyclePhases;
 
 } // namespace
 
 using namespace HTMLNames;
 
 PaintLayer::PaintLayer(LayoutBoxModelObject* layoutObject, PaintLayerType type)
     : m_layerType(type)
     , m_hasSelfPaintingLayerDescendant(false)
@@ skipping 2724 matching lines @@
 
 void showLayerTree(const blink::LayoutObject* layoutObject)
 {
     if (!layoutObject) {
         fprintf(stderr, "Cannot showLayerTree. Root is (nil)\n");
         return;
     }
     showLayerTree(layoutObject->enclosingLayer());
 }
 #endif